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Australian Herbicide Resistance Initiative (AHRI)

The north face of the Eiger

Tag Archives | mechanisms

Australian Herbicide Resistance Initiative (AHRI)

The north face of the Eiger

The mile of vertical limestone and ice that makes up the north face of the Eiger is the ultimate challenge for many mountain climbers, not necessarily due to its complexity, but because of the commitment. Once embarked on the ascent, that’s it, there is no turning back. Mountain climbers are a little different to most – they love to choose the most difficult path. Target site herbicide resistance is well understood because it is relatively easy to research, and the mutations often endow high levels of herbicide resistance. Metabolic herbicide resistance, on the other hand, is much more difficult to…

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Plants in pots

Australian Herbicide Resistance Initiative (AHRI)

How fit are you?

Within the AHRI research team we have a range of fitness levels. At one end of the scale we have Dr Roberto Busi, winner of the Perth marathon for two years running. Further down the scale we have Professor Stephen Powles who recently put his back out watching the World Cup final on television! Resistant weeds also have a range of fitness levels. In some cases, the resistance mechanism weakens the plant and it doesn’t grow quite as well as it once did. In other cases, the resistant plants are just as fit as their susceptible counterparts. Palmer amaranth in…

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Triple disc of machine for agriculture

Australian Herbicide Resistance Initiative (AHRI)

Never mix trifluralin and…

Mum – ‘blue and green should never be seen’ Wife – ‘never mix swirls and stripes’ Dad – ‘never drink on an empty stomach’ Sam Kleemann – ‘never mix trifluralin and a single disc seeder’. It will come as no surprise to many that researcher Sam Kleemann from the University of Adelaide found that trifluralin gave poor ryegrass control and reduced crop establishment when wheat was sown with a single disc opener in three trials between 2008 and 2012. Some growers favour single disc, zero till seeding because the lack of soil disturbance may reduce weed emergence. Sam observed this…

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Weeds sample in glass

Australian Herbicide Resistance Initiative (AHRI)

Turning up resistance genes

When you drink alcohol, it is broken down by P450 enzymes. This is one of the processes by which your body detoxifies the alcohol so it doesn’t kill you. We all have these enzymes, although some of us have more than others – which is why some people are a cheap date, while others are not so. In AHRI, we have known for some time that P450 genes are involved in metabolic herbicide resistant ryegrass, but we had no idea which genes were responsible, or how they were inherited from one generation to the next. Until now. AHRI researcher Todd…

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Wild radish flower

Australian Herbicide Resistance Initiative (AHRI)

Left jab, right hook

“Float like a butterfly sting like a bee – his hands can’t hit what his eyes can’t see.” Muhammad Ali. A good boxer uses combinations of punches to beat his opponent. A good farmer uses diverse combinations to beat weeds. Herbicides and crop competition are the left jabs, harvest weed seed control is the right hook that delivers the knock-out blow. In 2008, AHRI researcher Dr Michael Walsh and colleagues published a paper showing that 2,4-D resistant wild radish could be controlled by 2,4-D if there was elevated wheat crop competition. This demonstrates that if weeds are noticeably affected but…

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Piece of grass

Australian Herbicide Resistance Initiative (AHRI)

Just add water

It regulates Earth’s temperature, our bodies need it when we’re thirsty, and it covers about 70% of Earth’s surface. Water is essential for a number of reasons, and here is one more. Most Australian growers and agronomists would expect that 2.5 L/ha trifluralin or the full label rate of Sakura® would give between 70 and 90% ryegrass control in crop. However, research by Dr Catherine Borger (DAFWA Merredin, WA) has shown that it depends on how you apply it. Catherine found that ryegrass control with Trifluralin or Sakura® increased from 53% to 78% as the carrier volume increased from 30…

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Ryegrass under vines

Australian Herbicide Resistance Initiative (AHRI)

Double banger – glyphosate and paraquat resistant ryegrass

People who alternate between beer and wine on a night out still end up drunk. Unfortunately, alternating between glyphosate and paraquat could result in resistance to both. Last week in Australian rural media, we heard from Andrew Storrie (Australian Glyphosate Sustainability Working Group) who reported a population of ryegrass that is resistant to both paraquat and glyphosate in a vineyard in Western Australia. Very scary stuff! Is this a freak event that will only happen in vineyards or is it a warning sign for broad acre agriculture? AHRI researcher, Dr Roberto Busi published a paper in 2011 suggesting that perhaps…

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Weeds sample in glass

Australian Herbicide Resistance Initiative (AHRI)

How do weeds resist glyphosate?

If you ever find yourself in the situation where you are catering for a group of people, and you are wondering how much food to prepare, the best thing to do is to prepare a little extra, just in case. The last thing that you want to do is run out. Believe it or not, this is how some weeds resist glyphosate. They make an extra-large batch of the enzyme that glyphosate binds to, just in case. This way, if the weed is sprayed with glyphosate that inhibits some of the enzyme, there is still enough left for the plant…

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Man touching a plant

Australian Herbicide Resistance Initiative (AHRI)

AHRI Mythbusters – can 2,4-D induce resistance in ryegrass?

What if you accidently sprayed the wrong herbicide? Agronomists of yester-year developed a handy trick. They found that if they accidently sprayed an oat crop with Hoegrass® (diclofop-methyl), they could stop crop damage in its tracks if they quickly applied 2,4-D. The grand question is…does it actually work? The ‘myth’ says yes. What does the science say? The AHRI Mythbusters team got the answer! In this latest AHRI research, Dr Heping Han and others found that when they pre-treated ryegrass with 2,4-D amine it became resistant to Hoegrass®. This is likely due to 2,4-D causing a spike in P450 activity…

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Researcher looking at samples

Australian Herbicide Resistance Initiative (AHRI)

How do P450 enzymes cause resistance?

What is a P450? Is it a car from the 70’s that fits a 44 gallon drum in the boot? No, that would be a P76. A P450 is an enzyme that eats herbicides. In fact, there are literally hundreds of P450 enzymes and some of them can chew on some herbicides, resulting in enhanced herbicide metabolism (metabolic resistance). We are now seeing an increased effort around the world to better understand metabolic resistance involving P450 enzymes. In 2005, Dr Paul Neve showed that ryegrass could quickly develop resistance after being sprayed with low doses of Hoegrass® (diclofop). Some recent…

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